The unspoken assumption, shared by Democrats and Republicans, most liberals and most conservatives, behind President Bush's amnesty/guest worker plan to grant legal residency to 3 million illegal aliens from Mexico is that the Mexican and Hispanic vote is important. No one on either side of the political and ideological divide even pretends it's not politics that really drives the amnesty plan. But now there's new evidence from the Census Bureau that challenges the plan's common assumption—and implies that the whole scheme should be pitched in the trash.

“If there is one shared view” between strategists of both parties, Washington Post reporter Thomas Edsall wrote several weeks ago, before the amnesty scheme ever saw newsprint, “it is an agreement on the central importance of Hispanic voters.” Later, the Wall Street Journal wrote, “immigration captures the president's ambition to remake his party's image, to prove the compassion in his conservatism and, most basically, to win the votes of America's fastest growing demographic group—Hispanics, six in 10 of whom are of Mexican origin.” Most basically, however, the president's ambition just might be the path to political suicide.

A new analysis of Census Bureau data by demographic analyst Steven Sailer and published last week by United Press International suggests that today and by the year 2004 there just aren't and won't be enough real Hispanic voters, let alone Mexican-American voters, to make any difference to national candidates. There's no doubt the Hispanic portion of the general population—and of the electorate—is increasing and that eventually Hispanic voting strength will matter. But today and in the next four years, it doesn't.

The census figures show, according to Mr. Sailer, that the present portion of the voting population—people who actually cast votes in the last election—that's Mexican is only 3 percent. In 1996 it was 2.6 percent, and by 2004 it will be 3.5 percent. But the point is that it doesn't make very much difference.

The Hispanic part of the voting population is of course larger (not all Hispanics are Mexican). It grew from 3.6 percent in 1988 to 5.4 percent last year, and by 2004, it may reach 6 percent or more. Mr. Sailer concludes, “Although in the long term, Mexican-Americans—and Hispanics in general—are likely to wield massive influence, they probably will not play an outsized role in the 2004 election—in particular, they are unlikely to offer much aid to Bush's expected re-election bid.”

That conclusion is in flat contradiction to what GOP strategists have told themselves and the press. Mr. Sailer quotes Bush pollster Matthew Dowd's remark to The Washington Post that “we have to get somewhere between … 38 to 40 percent of the Hispanic vote” in 2004. “Yet,” Mr. Sailer notes, “simple math shows that if Bush boosts his share of the Hispanic vote from 35 percent to 40 percent, and Hispanics cast six percent of the votes in 2004, then Bush will gain a mere 0.3 percentage points overall.”

In addition to the facts and figures about voter population, the brute fact is that the Electoral College determines who wins presidential elections, as Mr. Bush and his advisers should have learned from the last one. And the other brute fact that Mr. Sailer notes is that electoral votes are determined not by how many voters you get but by how many states you win, and 72.3 of the entire Mexican-American population lives in two states: California and Texas. “Neither one is expected to be up for grabs in the next election.”

In California, where Mr. Bush won only 41.7 percent of the total vote last year, “Even if Bush had won 100 percent of the Mexican-American voters in California last November, he still would have lost California by around 400,000 votes,” Mr. Sailer writes.

Mr. Sailer's math is pretty compelling, but don't bet your tortillas that either the president or his political wizards are going to pay much attention. In the first place, the conviction that Republicans can't win without the Hispanics has become impervious to fact and reason in the Republican mind. Too much rhetoric, too many plans and resources have already been invested in making it come true for the obsession to be abandoned just because it's contradicted by facts.

And in the second place, there are other reasons for Mr. Bush's commitment to more immigration besides politics. The Big Business backbone of the GOP wants it, and Mr. Sailer himself notes yet another reason at the end of his article. “One political observer suggests a symbolic but politically potent reason: 'I think it goes back to Bush being nice to Hispanics to help him with suburban moderates, who don't like Republicans who are too mean spirited.' Because non-Hispanic whites cast four out of every five ballots, that might be the most sensible explanation.”

Well, it is an explanation. Whether it's sensible is quite a different question.